Bulk process for making maleimide copolymers

Abstract

A bulk process is provided for making maleimide copolymers. The process involves reacting a monomer mixture comprising a maleimide monomer compound, a vinyl aromatic compound and a vinyl cyanide compound in a continuous stirred tank reactor, and then further reacting the material in a plug flow reactor to obtain a desired conversion level, and then devolatizing the product. The process provides enhanced oligomer control and enhanced levels of glass transition temperature and other properties. The maleimide copolymer obtained by the process may be further blended with impact modifiers to produce thermoplastic compositions which are useful for making molded articles such as automotive parts for under the hood applications, such as distributor caps.

We claim: 
     
       1. A bulk process for making a maleimide copolymer product comprising the steps of: (a) reacting a maleimide monomer mixture in a continuous stirred tank reactor, said monomer mixture comprising a maleimide monomer and a comohomer selected from the group consisting of vinyl aromatic compounds, vinyl cyanide compounds and acrylate compounds to form a first product having a monomer conversion level of between 10 and 90 percent by weight based on the total weight of monomer in said monomer mixture,   (b) reacting said first product in a plug flow reactor to produce a second product having a monomer conversion level of at least 5 percent by weight greater than said first product based on the total weight of monomer in said monomer mixture, said second product having a monomer conversion level of between 50 and 95 percent by weight based on the total weight of said monomer mixture, and   (c) devolatilizing said second product to produce said maleimide copolymer product.   
     
     
       2. The process of claim 1 wherein said first product has a monomer conversion level of between 40 to 65 percent based on the total weight of the monomer in said monomer mixture. 
     
     
       3. The process of claim 1 wherein said first product has a monomer conversion level of between 50 to 55 percent based on the total weight of the monomer in said monomer mixture. 
     
     
       4. The process of claim 1 wherein said continuous stirred tank reactor has a residence time of between 1.0 and 10.0 hours. 
     
     
       5. The process of claim 1 wherein said continuous stirred tank reactor has a residence time of between 3.0 and 8.0 hours. 
     
     
       6. The process of claim 1 wherein samd continuous stirred tank reactor has a residence time of between 4.0 and 5.0 hours. 
     
     
       7. The process of claim 1.wherein said continuous stirred tank reactor has an average temperature of between 75° C. and 100° C. 
     
     
       8. The process of claim 1 wherein said continuous stirred tank reactor has an average temperature of between 80° C. and 95° C. 
     
     
       9. The process of claim 1 wherein said continuous stirred tank reactor has an average temperature of between 82° C. and 88° C. 
     
     
       10. The process of claim 1 wherein said plug flow reactor has a residence time of between 0.5 hours and 3.0 hours. 
     
     
       11. The process of claim 1 wherein said plug flow reactor has a residence time of between 1.0 hours and 2.0 hours. 
     
     
       12. The process of claim 1 wherein said plug flow reactor has a residence time of between 1.2 hours and 1.8 hours. 
     
     
       13. The process of claim 1 wherein said plug flow reactor has a feed zone, an intermediate zone and a final zone, said first product being fed into said first zone, said intermediate zone receiving material from said first zone, said intermediate zone having a temperature of between 100° C. and 120°, said final zone receiving material from said intermediate zone and said final zone having a temperature less than said intermediate zone, said final zone temperature being between 95° C. and 105° C. 
     
     
       14. The process of claim 1 wherein said second product has a monomer conversion level of between 60 and 80 percent by weight based on the total weight of the monomer mixture. 
     
     
       15. The process of claim 1 wherein said second product has a monomer conversion level of between 65 and 75 percent by weight based on the total weight of the monomer mixture. 
     
     
       16. The process of claim 1 wherein said maleimide copolymer product has a residual maleimide monomer level of less than 500 parts per million by weight based on the total weight of the maleimide copolymer. 
     
     
       17. The process of claim 1 wherein said maleimide copolymer has a glass transition temperature of at least 140° C. and a viscosity of less than 2000 poise at 260° C. and 1000 reciprocal second as measured by ASTM D3835. 
     
     
       18. The process of claim 1 wherein said monomer mixture comprises an initiator selected from the group consisting of azo initiators and peroxide initiators. 
     
     
       19. The process of claim 1 consisting essentially of said steps a, b and c. 
     
     
       20. The process of claim 1 wherein said monomer mixture comprises (i) a maleimide compound, (ii) a vinyl aromatic compound and (iii) a vinyl cyanide compound. 
     
     
       21. The process of claim 20 wherein said maleimide compound is present at a level of from 15 to 35 percent by weight based on the total weight of compounds (i), (ii) and (iii), said vinyl aromatic compound being present at a level of from 55 to 70 percent by weight based on the total weight of said compounds (i), (ii) and (iii), and said vinyl cyanide compound being present at a level of from 5 to 40 percent by weight based on the total weight of said compounds (i), (ii) and (iii).